When to raise a draw?

[SmallFish]

Hello,

I have a question regarding draws. When is it correct to raise and when is it correct to just call a drawing hand?

For example: I post in the cutoff and I am dealt a 10 [img]/images/graemlins/heart.gif[/img]8 [img]/images/graemlins/heart.gif[/img]

The flop comes up with 2 hearts and I have a flush draw.
Lets say there are 5 people that see the flop and the guy in LP bets and It's now up to me, Is raising or calling best here?

If i raise i knock people out and get a free card and if the flush hits I won't make as much, but If I call I keep the others in and I lose more if I don't hit my flush because I lost the free card opportunity.

Another Example

Lets say I am dealt K [img]/images/graemlins/club.gif[/img]10 [img]/images/graemlins/heart.gif[/img]

I see the flop with 4 others
The flop is Q [img]/images/graemlins/spade.gif[/img]J [img]/images/graemlins/heart.gif[/img]2 [img]/images/graemlins/diamond.gif[/img]

I bet, the person to my immedite left raises me, 2 others call and it is up to me again, Is this a raise or call here
and why?

If I reraise and don't hit my straight I have lost more than if I had just called, But if I re-raise I will gain 3 extra bets if the straight hits.

How do you calculate when it is best to pump a drawing hand or just become a clling station until it hits?

I am familair with outs pot odds and implied odds and can calculate them no problem but how do situations like this determine If a reraise or just calling is more profitable?